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中拐—五、八区是准噶尔盆地西北缘天然气勘探最为重要的区域。在综合分析天然气化学组分、稳定碳同位素及C7轻烃化合物特征的基础上,对该区二叠系天然气地球化学特征及分布规律进行了研究。从化学组成上看,可将该区天然气划分为低氮气含量的湿气和干气2种类型;从成因类型上看,有原油二次裂解形成的油型气、干酪根初次裂解形成的煤型气及二者的混源气等3种类型。根据不同成因类型天然气在纵向和横向上的分布特征,认为不整合面和断源断裂对于天然气的分布具有明显的控制作用,具体表现为:在二叠系佳木河组顶部不整合面附近地层内主要分布油型气与煤型气的混源气,而在较大规模的断源断裂附近易于富集煤型气;在不整合和断裂不发育的区域,风城组及其上覆地层中易于富集油型气,佳木河组则广泛分布煤型气。
Zhonggua - Area 5 and Area 8 are the most important areas for natural gas exploration in the northwestern margin of the Junggar Basin. Based on the comprehensive analysis of the characteristics of natural gas chemical composition, stable carbon isotopes and C7 light hydrocarbon compounds, the geochemical characteristics and distribution of natural gas in the Permian were studied. In terms of chemical composition, the natural gas in this area can be divided into two types: low nitrogen gas and dry gas. In terms of genetic type, oil gas formed by secondary cracking of crude oil and coal formed by kerogen pyrolysis for the first time Type gas and mixed gas of the three types. According to the vertical and horizontal distribution characteristics of natural gas of different genetic types, it is considered that unconformity and fault-source fracture have significant control over the distribution of natural gas, which is manifested in the following aspects: the formation near the unconformity at the top of the Jiamuhe Formation in the Permian Which mainly distributes mixed gas of oil-gas and coal-type gas, and is easy to enrich coal-gas in the vicinity of large-scale fault source faults. In areas where unconformity and fault rupture, the wind city formation and its overlying strata Easily enriched in oil-gas, Jiamu Group is widely distributed coal-type gas.